1. Field of Invention
The invention relates to an electrostatographic image forming apparatus employed in a copier, a facsimile, a laser printer and the like, and to a process unit, a photosensitive member cartridge and a developer cartridge that are for use in the image forming apparatus.
2. Description of Related Art
In some conventional image forming apparatuses for recording character or image data by supplying a developer to an electrostatic latent image formed on a photosensitive member (photosensitive drum) and transferring the visible image formed by the developer onto a recording medium, a cartridge-type process unit as disclosed in, for example, Japanese Patent Application Laid-open Nos. HEI 8-54786 and HEI 9-319285, (which correspond to U.S. Pat. Nos. 5,845,176 and 5,805,959, respectively) is employed in order to facilitate operations for maintenance, replacement, and the like.
In a conventional arrangement, after a photosensitive member cartridge having at least a photosensitive member is set into a body (housing) of an image forming apparatus, a developer cartridge having a developer containing chamber and a developing roller can be attached to or detached from the photosensitive member cartridge. In another conventional arrangement, a process unit in which a developer cartridge has been set with respect to a photosensitive member cartridge is set into the housing of an image forming apparatus.
The developing roller needs to be set so that the surface of the developing roller is pressed against the surface of the photosensitive member (photosensitive drum) during image forming operation. This arrangement is necessary to form a visible image on the photosensitive member (photosensitive drum) by supplying a thin layer of developer formed on the developing roller onto an electrostatic latent image that is formed on the surface of the photosensitive member.
However, in order to replace the photosensitive member cartridge due to deterioration thereof, or replace the developer cartridge due to exhaustion of developer (toner) or the like, the developing roller and the photosensitive member must be separated apart from each other and, after replacement, placed at adjacent positions. Therefore, during a replacement operation, there is a danger that the surface of the developing roller may impact the surface of the photosensitive member cartridge or the like. If such an impact occurs, component parts thereof may break, or the position of a developer cartridge support portion relative to the photosensitive member cartridge may deviate, so that uniform pressurization of the developing roller against the photosensitive member cannot be accomplished.
Further, the conventional technology requires that the handling of the developer cartridge be facilitated by simplifying the operation of setting the developer cartridge into the press contact with the photosensitive member cartridge, and the operation of removing the developer cartridge therefrom, as much as possible.